Management of the irritable bowel syndrome

Unbinding pathways of an agonist and an antagonist from the 5-HT3 receptor

The binding sites of 5-HT3 and other Cys-loop receptors have been extensively studied, but there are no data on the entry and exit routes of ligands for these sites. Here we have used molecular dynamics simulations to predict the pathway for agonists and antagonists exiting from the 5-HT3 receptor binding site. The data suggest that the unbinding pathway follows a tunnel at the interface of two subunits, which is approximately 8 A long and terminates approximately 20 A above the membrane. The exit routes for an agonist (5-HT) and an antagonist (granisetron) were similar, with trajectories toward the membrane and outward from the ligand binding site. 5-HT appears to form many hydrogen bonds with residues in the unbinding pathway, and experiments show that mutating these residues significantly affects function. The location of the pathway is also supported by docking studies of granisetron, which show a potential binding site for granisetron on the unbinding route. We propose that leaving the binding pocket along this tunnel places the ligands close to the membrane and prevents their immediate reentry into the binding pocket. We anticipate similar exit pathways for other members of the Cys-loop receptor family.

Performance of the EQ-5D in patients with irritable bowel syndrome

OBJECTIVE

The EQ-5D is a standardized, nondisease-specific instrument for evaluating patients' preference-based valuations of health-related quality of life (HRQoL). This study's purpose was to determine the psychometric properties of EQ-5D in patients with irritable bowel syndrome (IBS).

METHODS

Data from four European IBS studies were assessed: UK (n = 161 and n = 297), Spain (n = 503), and Germany (n = 100). The EQ-5D is a five-item health state descriptive system used to develop health states (EQ-5D(INDEX)) and a visual analog scale (VAS) (0-100 from worst to best imaginable health state, EQ-5D(VAS)). Measures used with the EQ-5D included the SF-36, Irritable Bowel Syndrome--Quality of Life (IBS-QOL), and both subjective and clinical global assessments of IBS. Convergent validity was assessed using SF-36 and IBS-QOL data, discriminant validity using global ratings of IBS severity, and responsiveness by subjective and physician assessment of condition.

RESULTS

Moderate-to-high associations (r >or= 0.33) were seen between the EQ-5D(VAS) and the SF-36 and IBS-QOL subscales. Mean response scores to EQ-5D(INDEX) dimensions and the EQ-5D(VAS) score were significantly better for control patients than for patients with IBS (all P < 0.01). The EQ-5D(VAS) was able to discriminate between levels of pain severity (quartiles, P < 0.001; mild/moderate/severe, P < 0.05) and general health severity (mild/moderate/severe, P < 0.001). The EQ-5D(VAS) and the EQ-5D(INDEX) were responsive in patients using both a self-perceived (Subject's Global Assessment) and physician-rated (Clinic Global Assessment) improvement.

CONCLUSIONS

The EQ-5D performs well in comparison to general and disease-specific outcomes. It is a valid and responsive measure that can be used to generate preference-based valuations of HRQoL in patients with IBS and useful for comparisons in clinical and cost-effectiveness studies.

Role of partially hydrolyzed guar gum in the treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is the world's most common gastrointestinal functional disorder and is associated with several social and economic costs. Health-related quality of life is often impaired in patients with IBS. The pathophysiologic mechanisms underlying IBS remain poorly defined. The therapeutic approach to patients with IBS is based on symptoms, and fibers may play an important role in treatment. Among the various types of fiber, water-soluble, non-gelling fibers seem to be a promising option for treatment of IBS. Partially hydrolyzed guar gum (PHGG) is a water-soluble, non-gelling fiber that has provided therapeutic benefits. In clinical trials, PHGG decreased symptoms in constipation-predominant and diarrhea-predominant forms of IBS and decreased abdominal pain. Further, an improvement in quality of life was observed in patients with IBS during and after treatment with PHGG. Moreover, PHGG seems to have prebiotic properties because it increases the colonic contents of short-chain fatty acids, Lactobacilli, and Bifidobacteria.

The role of fiber in the treatment of irritable bowel syndrome: therapeutic recommendations

Irritable bowel syndrome is a common clinical condition that often presents a therapeutic challenge. There is no standard therapy and a multilevel approach is recommended. A high-fiber diet is often one of these components. Many investigators have studied the effectiveness of either fiber supplementation or bulking agents in patients with irritable bowel syndrome. The purpose of this review is to summarize the current literature on the use of fiber in irritable bowel syndrome and to provide some specific recommendations. Systematic reviews of these trials have generally not found fiber to be significantly more effective than placebo at relieving global irritable bowel syndrome symptoms. There may be differences between results obtained with soluble and insoluble fiber. Adverse effects of fiber use may include abdominal discomfort and bloating. Although dietary fiber or bulking agents do not appear to be useful as sole treatment of irritable bowel syndrome, they may have a limited role in empiric therapy depending upon the patient's symptom complex, especially if constipation is the most significant symptom. The basic principles for using fiber therapy are to start with a low dose and increase slowly, to give an adequate trial and to evaluate the results early and periodically.

Role of corticotropin-releasing factor pathways in stress-related alterations of colonic motor function and viscerosensibility in female rodents

BACKGROUND

Clinical reports have shown that irritable bowel syndrome (IBS) is comorbid with anxiety/depression and stress-related events, and that the disorder is more prevalent among women than among men. In rodents, colorectal distention (CRD) induces abdominal contractions, and this visceromotor response is used to assess visceral pain. The activation of brain corticotropin-releasing factor (CRF) pathways has a key role in the behavioral and visceral responses to stress.

OBJECTIVE

In this review of experimental studies that delineate the underlying mechanisms of the stress response, we focused on CRF signaling pathways and sex hormones in modulating visceral hypersensitivity induced by CRD in rodents.

METHODS

The findings of our recent research on the development of an experimental model of visceral pain in female rats and the modulation of the hyperalgesic response to CRD by CRF antagonists were integrated with those of the published literature. A MEDLINE search of the years 1981 to 2005 was conducted using the key words stress, CRF, CRH, CRF1 receptor, IBS, CRD, female rat, visceral pain, estrogen, and anxiety.

RESULTS

CRF and other related mammalian peptides (urocortins) interact with the distinct CRF subtype 1 and 2 receptors. Well-documented preclinical studies have established the role of brain CRF1 receptors in mediating stress-related anxiogenic and visceral (stimulation of colonic motor function and sensitization to repeated CRD) responses in male rodents, whereas more limited studies have been performed in female rats. Our recent study indicated that the CRF1 antagonist antalarmin prevents visceral hypersensitivity induced by 2 sets of CRD in female rats. In several models of visceral pain induced by CRD, sex differences and a sensitization action of estrogen were reported. Our preliminary evidence indicated a potentiating interaction between CRF-CRF1 pathways and estrogen in the stimulation of colonic motor responses that may take place within the enteric neurons of the colon, where both CRF1 and estrogen receptors are present.

CONCLUSIONS

The results of this review suggest that overactivity of CRF1 signaling in the brain and the gut may have relevance in understanding the comorbidity of anxiety/depression and IBS in diarrhea-predominant female patients. Targeting these mechanisms with CRF1 antagonists may provide a novel therapeutic strategy.

Functional gastrointestinal disorders and mast cells: implications for therapy

The pathophysiology of functional gastrointestinal disorders is poorly understood. Accepted common mechanisms include psychosocial factors, abnormal gastrointestinal motility and disturbed visceral sensory perception, but the underlying causes remain unclear. Mast cells (MCs) are immunocytes widely distributed throughout the gastrointestinal tract. Several stimuli (e.g. allergens, neuropeptides and stress) lead to MC activation with consequent mediator release (e.g. histamine, tryptase and prostanoids). The MC mediators interact with nerves supplying the gut leading to altered gut physiology and increased sensory perception. The intestinal mucosa of irritable bowel syndrome patients contains on average an increased number of MCs. These cells release an increased amount of mediators in close vicinity to mucosal innervation. The MC activation and their close proximity to nerve fibres is correlated with the severity of perceived abdominal painful sensations. These data provide a strong basis for considering MCs as important participants in visceral hypersensitivity and pain perception in irritable bowel syndrome. Inhibition of MC function may ameliorate irritable bowel symptoms. Novel drugs with an increased potential in the control of MC function (e.g., anti-IgE antibodies, the intracellular protein tyrosine kinase inhibitor Syk) and mediator release (e.g., second generation antihistamines, proteinase-activated receptor antagonists) may be useful pharmacological tools for these common disorders.

Nutrition and motility disorders

The purpose of this article is to give an overview of the relation between feeding and gastrointestinal symptoms and complaints, and to review different motility disorders that have implications for food intake. We also report the consequences for nutrition state and the evidence-based principles of dietary modification in patients with motility disorders.

A symptom-based approach to making a positive diagnosis of irritable bowel syndrome with constipation

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder. Characterised by abdominal pain or discomfort, bloating and altered bowel habit, IBS is a chronic recurring condition, typically affecting up to 15% of the Western population, IBS can be subclassified into IBS with constipation (IBS-C), IBS with diarrhoea (IBS-D), or IBS with alternating constipation or diarrhoea symptoms (IBS-A). Conventional clinical diagnosis focuses on excluding all potential organic causes of patient symptoms. However, a positive diagnosis of IBS may be established using published criteria such as the Manning and/or Rome criteria. While these methods are useful to identify patients with IBS who are suitable for enrollment into clinical trials, the criteria are relatively complex and not readily applicable to general practice. In this review we present an 'identify, eliminate, probe' algorithm that may be appropriate to establish a positive diagnosis of patients with IBS-C, as symptoms characteristic of patients in this IBS subgroup are least likely to be confused with symptoms reflecting serious organic disease.

Symptom overlap and comorbidity of irritable bowel syndrome with other conditions

Irritable bowel syndrome (IBS) is one of several highly prevalent, multi-symptom gastrointestinal motility disorders that have a wide clinical spectrum and are associated with symptoms of gastrointestinal dysmotility and visceral hypersensitivity. Symptom overlap and comorbidity between IBS and other gastrointestinal motility disorders (eg, chronic constipation, functional dyspepsia, gastroesophageal reflux disease), with gastrointestinal disorders that are not related to motility (eg, celiac disease, lactose intolerance), and with somatic conditions (eg, fibromyalgia, chronic fatigue syndrome), are frequent. The clinical associations and pathophysiologic links between IBS and these disorders continue to be explored. This review discusses overlapping symptoms and comorbidity of IBS with select gastrointestinal and non-gastrointestinal disorders and attempts to identify commonalities among these conditions.

Assessment of visceral sensitivity using radio telemetry in a rat model of maternal separation

Stress plays an important role in the development of visceral hypersensitivity, a key mechanism underlying the pathophysiology of the irritable bowel syndrome. Visceral sensitivity in rats is generally assessed under restrain conditions. To avoid this potential stress factor, we developed a model using implanted radio telemetry for remote measurement of the visceromotor response (VMR) to colorectal distention (CRD). Ten days after implantation of a radio telemetry transmitter and EMG electrodes, visceral sensitivity was evaluated by applying a standardized distension protocol (1, 1.5 and 2 mL) on three different days. In a second series, visceral sensitivity was assessed in maternally separated rats before, directly after and at 6 and 24 h after water avoidance (WA) stress. CRD resulted in a reproducible VMR response on the three different study days. In separated but not in non-handled rats, WA significantly increased visceral sensitivity at 6 h (P=0.006) and 24 h (P=0.004) after WA. Our results show that radio telemetry is a reliable and well tolerated new tool for evaluating visceral sensitivity in rats. These data further confirm that maternal separation is a good model for evaluating the mechanisms underlying visceral hypersensitivity.

Barostat testing of rectal sensation and compliance in humans: comparison of results across two centres and overall reproducibility

We assessed reproducibility of measurements of rectal compliance and sensation in health in studies conducted at two centres. We estimated samples size necessary to show clinically meaningful changes in future studies. We performed rectal barostat tests three times (day 1, day 1 after 4 h and 14-17 days later) in 34 healthy participants. We measured compliance and pressure thresholds for first sensation, urgency, discomfort and pain using ascending method of limits and symptom ratings for gas, urgency, discomfort and pain during four phasic distensions (12, 24, 36 and 48 mmHg) in random order. Results obtained at the two centres differed minimally. Reproducibility of sensory end points varies with type of sensation, pressure level and method of distension. Pressure threshold for pain and sensory ratings for non-painful sensations at 36 and 48 mmHg distension were most reproducible in the two centres. Sample size calculations suggested that crossover design is preferable in therapeutic trials: for each dose of medication tested, a sample of 21 should be sufficient to demonstrate 30% changes in all sensory thresholds and almost all sensory ratings. We conclude that reproducibility varies with sensation type, pressure level and distension method, but in a two-centre study, differences in observed results of sensation are minimal and pressure threshold for pain and sensory ratings at 36-48 mmHg of distension are reproducible.

Technology insight: calprotectin, lactoferrin and nitric oxide as novel markers of inflammatory bowel disease

Distinguishing patients with inflammatory bowel disease from those with irritable bowel syndrome can be difficult. A simple and reliable test that detects intestinal inflammation would therefore be very useful in the clinic. If such a test parameter correlated with the intensity of the inflammatory reaction it could also be used to monitor disease activity. Calprotectin, lactoferrin and nitric oxide are produced and released locally in much greater quantities in the inflamed gut than in the noninflamed gut. These compounds can be readily measured in fecal samples (calprotectin and lactoferrin) or directly in the intestinal lumen (nitric oxide gas). Here, we discuss what is known about these markers, how they could be used in clinical practice and how they can complement existing techniques used for the diagnosis and monitoring of inflammatory bowel disease.

The effect of fluoxetine in patients with pain and constipation-predominant irritable bowel syndrome: a double-blind randomized-controlled study

BACKGROUND

Irritable bowel syndrome has been treated with selective serotonin reuptake inhibitors but there is not enough evidence from controlled trials to prove their effectiveness.

AIM

To compare the effects of fluoxetine and placebo in the treatment of pain and constipation-predominant irritable bowel syndrome in a double-blind randomized-controlled trial.

METHODS

Forty-four cases meeting Rome II criteria for irritable bowel syndrome with predominance of pain and constipation were included in this study. Organic causes were ruled out by detailed history, physical examination, laboratory tests and colonoscopy. Participants were then randomly assigned to receive either fluoxetine or placebo for 12 weeks. Symptoms addressed by the Rome II criteria were recorded during treatment and 4 weeks after termination of treatment.

RESULTS

Fluoxetine was significantly more effective than placebo in decreasing abdominal discomfort, relieving feeling and sense of bloating, increasing frequency of bowel movements and decreasing consistency of stool. Mean number of symptoms per patient decreased from 4.6 to 0.7 in the fluoxetine group vs. 4.5 to 2.9 in controls (P < 0.001).

CONCLUSIONS

Fluoxetine is an effective and well-tolerated short-term treatment for pain and constipation-predominant irritable bowel syndrome.

Serotonin transporter function and expression are reduced in mice with TNBS-induced colitis

Regulated release of serotonin (5-HT) from enterochromaffin (EC) cells activates neural reflexes that are involved in gut motility, secretion, vascular perfusion and sensation. The 5-HT-selective reuptake transporter (SERT) terminates serotonergic signalling in the intestinal mucosa. The aim of this investigation was to determine whether mucosal 5-HT content, release, and/or reuptake are altered in a murine model of immune cell-mediated colitis. Experiments were conducted 6 days after colitis was induced by 2,4,6-trinitrobenzene sulfonic acid, a time point when macroscopic and histological damage scores indicated significant inflammation. During inflammation, SERT transcript levels and immunoreactivity were reduced, and the uptake of [3H] 5-HT was impaired. Increases in mucosal 5-HT content and the number of 5-HT-immunoreactive mast cells in the lamina propria were also detected in the inflamed region, whereas EC cell numbers did not change. Mucosal 5-HT released under basal and stimulated conditions was unchanged in animals with colitis. These data suggest that murine colitis alters 5-HT signalling by increasing 5-HT availability through decreased 5-HT uptake by mucosal epithelial cells. These findings support the concept that altered 5-HT signalling could be a contributing factor in altered gut function and sensitivity in inflammatory bowel disease.

The use of Lactobacillus GG in irritable bowel syndrome in children: a double-blind randomized control trial

OBJECTIVE

To determine whether oral administration of the probiotic Lactobacillus GG under randomized, double-blinded, placebo-controlled conditions would improve symptoms of irritable bowel syndrome (IBS) in children.

STUDY DESIGN

Fifty children fulfilling the Rome II criteria for IBS were given Lactobacillus GG or placebo for 6 weeks. Response to therapy was recorded and collected on a weekly basis using the Gastrointestinal Symptom Rating Scale (GSRS).

RESULTS

Lactobacillus GG was not superior to placebo in relieving abdominal pain (40.0% response rate in the placebo group vs 44.0% in the Lactobacillus GG group; P=.774). There was no difference in the other gastrointestinal symptoms, except for a lower incidence of perceived abdominal distention (P=.02 favoring Lactobacillus GG).

CONCLUSIONS

Lactobacillus GG was not superior to placebo in the treatment of abdominal pain in children with IBS but may help relieve such symptoms as perceived abdominal distention.

Relationship between symptoms and hypersensitivity to rectal distension in patients with irritable bowel syndrome

BACKGROUND

Visceral hypersensitivity is considered an important pathophysiological mechanism in irritable bowel syndrome, yet its relationship to symptoms is unclear.

AIM

To detect possible associations between symptoms and the presence of hypersensitivity to rectal distension in patients with irritable bowel syndrome.

METHODS

Ninety-two irritable bowel syndrome patients and 17 healthy volunteers underwent a rectal barostat study. The association between specific irritable bowel syndrome symptoms and the presence of hypersensitivity was examined using Area under the Receiver Operating Characteristic curves.

RESULTS

Irritable bowel syndrome patients had significantly lower thresholds for discomfort/pain than healthy volunteers: 24 (18-30) and 30 (27-45) mmHg above minimal distending pressure, respectively. Forty-one patients (45%) showed hypersensitivity to rectal distension. Proportions of patients with different predominant bowel habits were similar in hypersensitive and normosensitive subgroups (diarrhoea predominant: 39 and 41%, respectively; alternating type: 27 and 28%, respectively; constipation predominant: 34 and 31%, respectively). Severe abdominal pain was more frequent in hypersensitive, compared with normosensitive patients (88% vs. 67%, P = 0.02), but none of the individual irritable bowel syndrome symptoms could accurately predict the presence of hypersensitivity, as assessed by Area under the Receiver Operating Characteristic curve analysis.

CONCLUSIONS

Hypersensitive and normosensitive irritable bowel syndrome patients present with comparable, heterogeneous symptomatology. Therefore, selection based on clinical parameters is unlikely to discriminate individual irritable bowel syndrome patients with visceral hypersensitivity from those with normal visceral sensitivity.

New and emerging treatments for irritable bowel syndrome and functional dyspepsia

The symptomatic management of irritable bowel syndrome (IBS) and functional dyspepsia, which often overlap, can be frustrating and difficult. Education and reassurance remain central for management although controlled trials are lacking. Psychological interventions may be useful in select patients but methodological inadequacies in clinical trials limit their interpretability. For symptom exacerbations, drug treatment is reasonable but no current treatment successfully targets the full symptom complex. Bulking agents are not of proven efficacy in IBS; they may improve constipation but worsen bloating and pain. Anticholinergics are of uncertain value in IBS. A meta-analysis of trials of smooth muscle relaxants for IBS has been reported to be positive but the quality of the trials included was poor. Antidepressants for IBS and functional dyspepsia appear to be efficacious based on the limited published evidence; both global symptoms and abdominal pain improve. Selective serotonin reuptake inhibitors (SSRIs) are of uncertain efficacy but anecdotally appear to be useful. Laxatives are not of proven efficacy in IBS. Loperamide improves diarrhea, but not abdominal pain in IBS. No drug is of proven efficacy for bloating. Acid suppression remains the mainstay of therapy for functional dyspepsia but the majority of patients do not have an adequate response. Promising drugs include new prokinetics for constipation-predominant IBS (e.g., tegaserod, a partial 5-HT4 agonist, prucalopride, a full 5-HT4 agonist, and dexloxiglumide, a cholecystokinin1 antagonist), agents for diarrhea-predominant IBS (e.g., 5-HT3 antagonists, alpha2 receptor agonists and corticotrophin receptor-1 antagonists), other visceral analgesics (e.g. tachykinin antagonists, opioid agonists) and in dyspepsia fundus relaxing agents (e.g., 5-HT1 agonists, tegaserod).

Gender difference on the symptoms, health-seeking behaviour, social impact and sleep quality in irritable bowel syndrome: a Rome II-based survey in an apparent healthy adult Chinese population in Taiwan

BACKGROUND

Little is known about the gender effect on irritable bowel syndrome in Asia.

AIM

To assess the gender difference in Chinese subjects with irritable bowel syndrome meeting Rome II criteria.

METHODS

Irritable bowel syndrome was identified from an apparently healthy adult population receiving a routine health maintenance program (n = 2018).

RESULTS

Female gender is not a factor associated with irritable bowel syndrome or irritable bowel syndrome-related health care-seeking behaviour. Female irritable bowel syndrome subjects, irrespective of consulting behaviour for irritable bowel syndrome, are likely to have < 3 bowel movements/week, hard/lumpy stools and abdominal fullness/bloating (P < 0.05). Female irritable bowel syndrome subjects are prone to be absent from school/work with more days of absenteeism, irrespective of consultation status (P < 0.05). Only female irritable bowel syndrome consulters have more absenteeism for their irritable bowel syndrome-related symptoms, reporting more sleep disturbances than their male counterparts (P < 0.001).

CONCLUSIONS

In an apparent healthy adult population in Taiwan, gender difference is present in Rome II defined Chinese subjects with irritable bowel syndrome as regards bowel symptoms, social impact and sleep quality. Female predominance was not found in irritable bowel syndrome subjects and irritable bowel syndrome-related health care-seeking behaviour in the current population. Both irritable bowel syndrome non-consulters and consulters have similar gender difference profiles in presenting symptoms, suggesting that bowel symptoms per se may not be the only factor leading to health care-seeking behaviour. The gender differences in sleep problems were observed solely in irritable bowel syndrome consulter.

Differential chemosensory function and receptor expression of splanchnic and pelvic colonic afferents in mice

Lumbar splanchnic (LSN) and sacral pelvic (PN) nerves convey different mechanosensory information from the colon to the spinal cord. Here we determined whether these pathways also differ in their chemosensitivity and receptor expression. Using an in vitro mouse colon preparation, individual primary afferents were tested with selective P2X and transient receptor potential vanilloid receptor 1 (TRPV1) receptor ligands. Afferent cell bodies in thoracolumbar and lumbosacral dorsal root ganglia (DRG) were retrogradely labelled from the colon and analysed for P2X3- and TRPV1-like immunoreactivity (LI). Forty per cent of LSN afferents responded to alpha,beta-methylene adenosine 5'-triphosphate (alpha,beta-meATP; 1 mm), an effect that was concentration dependent and reversed by the P2X antagonist pyridoxyl5-phosphate 6-azophenyl-2',4'-disulphonic acid (PPADS) (100 microm). Significantly fewer PN afferents (7%) responded to alpha,beta-meATP. Correspondingly, 36% of colonic thoracolumbar DRG neurones exhibited P2X3-LI compared with only 19% of colonic lumbosacral neurones. Capsaicin (3 microm) excited 61% of LSN afferents and 47% of PN afferents; 82% of thoracolumbar and 50% of lumbosacral colonic DRG neurones displayed TRPV1-LI. Mechanically insensitive afferents were recruited by alpha,beta-meATP or capsaicin, and were almost exclusive to the LSN. Capsaicin-responsive LSN afferents displayed marked mechanical desensitization after responding to capsaicin, which did not occur in capsaicin-responsive PN afferents. Therefore, colonic LSN and PN pathways differ in their chemosensitivity to known noxious stimuli and their corresponding receptor expression. As these pathways relay information that may relate to symptoms in functional gastrointestinal disease, these results may have implications for the efficacy of therapies targeting receptor modulation.

Rectal instillation of butyrate provides a novel clinically relevant model of noninflammatory colonic hypersensitivity in rats

BACKGROUND & AIMS

The treatment of irritable bowel syndrome (IBS), characterized by abdominal pain and bloating, is empirical and often poorly efficient. Research lacks suitable models for studying the pathophysiologic mechanisms of the colonic hypersensitivity and new pharmacologic targets. The present study aimed to develop a novel model of colonic hypersensitivity possessing several of the characteristics encountered in patients with IBS.

METHODS

Rats received enemas of a butyrate solution (8-1000 mmol/L) twice daily for 3 days. A time course was determined for colonic hypersensitivity (colorectal distention test) and referred cutaneous lumbar hyperalgesia (von Frey hairs). Macroscopic and histologic analyses were performed on colonic mucosa. The efficacy of morphine, U50488H (a kappa opioid agonist), and trimebutine on the 2 pain parameters was determined. Finally, the involvement of peptidergic C-fibers was evaluated using capsaicin-pretreated animals and treatments with calcitonin gene-related peptide (CGRP) and neurokinin 1 receptor antagonists.

RESULTS

Butyrate enemas induced a sustained, concentration-dependent colonic hypersensitivity and, to a lesser extent, a referred cutaneous mechanical hyperalgesia, particularly in female rats, but no macroscopic and histologic modifications of the colonic mucosa, as observed in patients with IBS. Both pain parameters were sensitive to morphine, U50488H, trimebutine, neonatal capsaicin treatment, and the CGRP receptor antagonist but not to the neurokinin 1 receptor antagonist.

CONCLUSIONS

These results present our noninflammatory model of chronic colonic hypersensitivity as a useful novel tool for studying IBS. The CGRP receptor antagonist-induced reduction of colonic hypersensitivity suggests that CGRP receptors may provide a promising target for treatment of IBS.

Treatment effects of partially hydrolyzed guar gum on symptoms and quality of life of patients with irritable bowel syndrome. A multicenter randomized open trial

The effects of partially hydrolyzed guar gum (PHGG) were compared in patients with irritable bowel syndrome, at 10 g/day (N = 40) and 5 g/day (N = 46) for 12 weeks. Gastrointestinal symptoms (GSRS), quality of life (SF-36), and psychological symptoms (HADS) were evaluated at baseline, during treatment (months 1 and 3), and at follow-up (month 6). In both groups symptoms and quality of life improved significantly after the first month of administration until follow-up compared to those at baseline. However, the improvement was significantly reduced at follow-up compared to the end of treatment. PHGG was effective for improving somatic (gastrointestinal symptoms) and psychological (quality of life and psychological distress) symptoms over the short term. Since the improvement tended to decrease after the end of the treatment period, further studies should evaluate the benefits of PHGG at a maintenance dosage.

Irritable bowel syndrome in the United States: prevalence, symptom patterns and impact

BACKGROUND

The impact of irritable bowel syndrome, a gastrointestinal motility disorder, is underestimated and poorly quantified, as clinicians may see only a minority of sufferers.

AIM

To determine the prevalence, symptom patterns and impact of irritable bowel syndrome in the US.

METHODS

This two-phase community survey used quota sampling and random-digit telephone dialing (screening interview) to identify individuals with medically diagnosed irritable bowel syndrome or individuals not formally diagnosed, but fulfilling irritable bowel syndrome diagnostic criteria (Manning, Rome I or II). Information on irritable bowel syndrome symptoms, general health status, lifestyle and impact of symptoms on individuals' lives was collected using in-depth follow-up interviews. Data were also collected for healthy controls identified in the screening interviews.

RESULTS

The total prevalence of irritable bowel syndrome in 5009 screening interviews was 14.1% (medically diagnosed: 3.3%; undiagnosed, but meeting irritable bowel syndrome criteria: 10.8%). Abdominal pain/discomfort was the most common symptom prompting consultation. Most sufferers (74% medically diagnosed; 63% undiagnosed) reported alternating constipation and diarrhoea. Previously diagnosed gastrointestinal disorders occurred more often in sufferers than non-sufferers. Irritable bowel syndrome sufferers had more days off work (6.4 vs. 3.0) and days in bed, and reduced activities to a greater extent than non-sufferers.

CONCLUSIONS

Most (76.6%) irritable bowel syndrome sufferers in the US are undiagnosed. Irritable bowel syndrome has a substantial impact on sufferers' well-being and health, with considerable socioeconomic consequences.

Serotonin excites neurons in the human submucous plexus via 5-HT3 receptors

BACKGROUND & AIMS

Serotonin (5-hydroxytryptamine [5-HT]) is a key signaling molecule in the gut. Recently, the neural 5-HT3 receptor received a lot of attention as a possible target in functional bowel diseases. Yet, the 5-HT3 receptor-mediated changes in properties of human enteric neurons is unknown.

METHODS

We used a fast imaging technique in combination with the potentiometric dye 1-(3-sulfonatopropyl)-4-[beta[2-(di-n-octylamino)-6-naphthyl]vinyl]pyridinium betaine to monitor directly the membrane potential changes in neurons of human submucous plexus from surgical specimens of 21 patients. An Ussing chamber technique was used to study 5-HT3 receptor involvement in chloride secretion.

RESULTS

Local microejection of 5-HT directly onto ganglion cells resulted in a transient excitation of enteric neurons characterized by increased spike discharge. This response was mimicked by the 5-HT3 receptor agonist, 2-methyl-5-HT, and blocked by the 5-HT3 receptor antagonist, tropisetron. The proportions of 5-HT-responsive nerve cells per ganglion ranged from 25.5% +/- 18.4% in the duodenum to 54.2% +/- 46.9% in the colon. Interestingly, 2-methyl-5-HT did not evoke chloride secretion in the human intestine but it did in the guinea-pig intestine. Specific 5-HT3A and 5-HT3B receptor subunit immunoreactivity as well as 5-HT3A and 5-HT3B receptor-specific messenger RNA were detected in the tissue samples. Based on co-labeling with the pan-neuronal marker HuC/D we conclude that submucous nerve cells potentially express heteromeric 5-HT3A/B receptors.

CONCLUSIONS

We show that 5-HT excited human enteric neurons via 5-HT3 receptors, which may comprise both 5-HT3A and 5-HT3B receptor subunits.

Lactobacillus and bifidobacterium in irritable bowel syndrome: symptom responses and relationship to cytokine profiles

BACKGROUND & AIMS

The aim of this study was to compare the response of symptoms and cytokine ratios in irritable bowel syndrome (IBS) with ingestion of probiotic preparations containing a lactobacillus or bifidobacterium strain.

METHODS

Seventy-seven subjects with IBS were randomized to receive either Lactobacillus salivarius UCC4331 or Bifidobacterium infantis 35624, each in a dose of 1 x 10 10 live bacterial cells in a malted milk drink, or the malted milk drink alone as placebo for 8 weeks. The cardinal symptoms of IBS were recorded on a daily basis and assessed each week. Quality of life assessment, stool microbiologic studies, and blood sampling for estimation of peripheral blood mononuclear cell release of the cytokines interleukin (IL)-10 and IL-12 were performed at the beginning and at the end of the treatment phase.

RESULTS

For all symptoms, with the exception of bowel movement frequency and consistency, those randomized to B infantis 35624 experienced a greater reduction in symptom scores; composite and individual scores for abdominal pain/discomfort, bloating/distention, and bowel movement difficulty were significantly lower than for placebo for those randomized to B infantis 35624 for most weeks of the treatment phase. At baseline, patients with IBS demonstrated an abnormal IL-10/IL-12 ratio, indicative of a proinflammatory, Th-1 state. This ratio was normalized by B infantis 35624 feeding alone.

CONCLUSIONS

B infantis 35624 alleviates symptoms in IBS; this symptomatic response was associated with normalization of the ratio of an anti-inflammatory to a proinflammatory cytokine, suggesting an immune-modulating role for this organism, in this disorder.

Visceral sensitivity and symptoms in patients with constipation- or diarrhea-predominant irritable bowel syndrome (IBS): effect of a low-fat intraduodenal infusion

BACKGROUND

Visceral hypersensitivity is common in Irritable Bowel Syndrome (IBS) patients, and symptoms exacerbate postprandially. Yet the effects of nutrients on visceral sensitivity and symptoms in these patients have not been fully explored.

AIMS

To evaluate the differences of visceral sensitivity and symptoms in healthy subjects and IBS patients during fasting and intraduodenal lipids infusion.

METHODS

Graded rectal distensions at fixed tension levels were performed in 16 IBS patients (8 IBS-C and 8 IBS-D) and 6 healthy subjects before and during intraduodenal lipids infusion at 0.5 kcal/min. Tension levels were increased in 4 gr increments up to 64 gr or discomfort during both conditions. At each step, perception and symptoms were measured by means of a validated questionnaire.

RESULTS

In basal conditions, perception thresholds in IBS patients and health were, respectively, 8 +/- 2 gr versus 32 +/- 9 gr (p < 0.001) with no changes during lipids. Intraduodenal lipids infusion significantly lowered threshold of discomfort in IBS patients in comparison to fasting (24 +/- 6 gr vs 34 +/- 4 gr; p < 0.05), while health tolerated all distension without discomfort. No differences of compliance, perception, or discomfort were observed between the two subgroups of patients at each tension step. The predominant symptom elicited in patients with IBS-C was abdominal pain (54%), while patients with IBS-D exhibited urgency (63%, p < 0.005); this pattern was maintained during lipids.

CONCLUSIONS

Intraduodenal lipids increase visceral sensitivity in both IBS-C and IBS-D; symptoms specificity in response to rectal distension is maintained in the postprandial period. Lipids may be responsible for the postprandial symptoms exacerbation in IBS.

Composition and temporal stability of gastrointestinal microbiota in irritable bowel syndrome--a longitudinal study in IBS and control subjects

Irritable bowel syndrome (IBS) is a common intestinal disorder that includes continuous or recurrent intestinal pain and discomfort and altered bowel habits. The pathophysiology of IBS is incompletely understood, but it may involve an altered intestinal microbiota. The aim of the present study was to compare the composition and temporal stability of faecal microbiota of IBS patients and healthy controls by applying culture-based techniques and PCR-DGGE analysis. No difference in the prevalence or mean culturable manners of bacteroides, bifidobacteria, spore-forming bacteria, lactobacilli, enterococci or yeasts were observed between the IBS and the control groups, whereas slightly higher numbers of coliforms as well as an increased aerobe:anaerobe ratio was observed in the IBS group. PCR-DGGE revealed more temporal instability in the predominant bacterial population of IBS subjects than in controls. In 9 out of 21 IBS subjects and 5 out of 17 controls the PCR-DGGE profiles obtained from the samples of the same individual on different occasions (sampling points 0, 3 and 6 months) were clearly different. However, the instability in some of the IBS subjects could partly be explained by the antibiotic consumption during the study. The present study suggests that instability of intestinal microbiota may be involved in IBS. However, further studies are needed to associate the instability with specific IBS symptoms or with specific bacterial groups and species.

Isolation and receptor profiling of ileal enterochromaffin cells

AIM AND METHODS

Enterochromaffin (EC) cells, interspersed throughout the gastrointestinal mucosa, provide most of the serotonin of the body and control intestinal motility, secretion and absorption. We purified EC cells from the rat ileum by a combination of elutriation and density gradient centrifugation in order to characterize the function of this important cell type.

RESULTS

Immunostaining showed that there were 84% serotonin-positive cells in the highly enriched EC fraction as compared with 12% in unfractionated cells, yielding a approximately sevenfold enrichment. Serotonin measurements in the cell suspensions indicated a seven to 14-fold enrichment. Presence of alpha- and beta-adrenoreceptor isoforms, muscarinic M3 and gama-aminobutyric acid (GABA)-A receptors was confirmed by RT-PCR and cytochemistry. Increased expression of VMAT-1 and GABA-A mRNA was also shown by quantitative TaqMan PCR using EC cell RNA. Serotonin release in isolated EC cells was stimulated by noradrenaline, and to a smaller extent, by carbachol, while GABA addition was without effect.

CONCLUSION

Our data provide a basis for a new approach to characterize receptors on this unique cell type.

The ion channel ASIC1 contributes to visceral but not cutaneous mechanoreceptor function

BACKGROUND & AIMS

Visceral mechanoreceptors are critical for perceived sensations and autonomic reflex control of gastrointestinal function. However, the molecular mechanisms underlying visceral mechanosensation remain poorly defined. Degenerin/epithelial Na+ channel (DEG/ENaC) family ion channels are candidate mechanosensory molecules, and we hypothesized that they influence visceral mechanosensation. We examined the influence of the DEG/ENaC channel ASIC1 on gastrointestinal mechanosensory function, on gastric emptying, and on fecal output. We also compared its role in gastrointestinal and somatic sensory function.

METHODS

To assess the role of ASIC1 we studied wild-type and ASIC1-/- mice. Reverse-transcription polymerase chain reaction (RT-PCR) and Western blot analysis determined expression of ASIC1 messenger RNA and protein in vagal and spinal sensory ganglia. Colonic, gastroesophageal, and cutaneous afferent fibers were characterized by functional subtype and their mechanical stimulus-response relationships were determined. Gastric emptying was determined by using a 13CO2 breath test. Behavioral tests assessed somatic mechanical and thermal sensitivity.

RESULTS

ASIC1 was expressed in sensory ganglia and was lost after disruption of the ASIC1 gene. Loss of ASIC1 increased mechanosensitivity in all colonic and gastroesophageal mechanoreceptor subtypes. In addition, ASIC1-/- mice showed almost double the gastric emptying time of wild-type mice. In contrast, loss of ASIC1 did not affect function in any of the 5 types of cutaneous mechanoreceptors, nor did it affect paw withdrawal responses or fecal output.

CONCLUSIONS

ASIC1 influences visceral but not cutaneous mechanoreceptor function, suggesting that different mechanisms underlie mechanosensory function in gut and skin. The role of ASIC1 is highlighted by prolonging gastric emptying of a meal in ASIC1-/- animals.

Suicidal ideation in patients with irritable bowel syndrome

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) traditionally is considered as more of a nuisance than having especially serious consequences. However, this is not the picture witnessed in tertiary care where we have encountered some tragic cases, prompting an assessment of suicidal ideation in such patients.

METHODS

One hundred follow-up, tertiary care IBS (tIBS) patients were compared with 100 secondary IBS (sIBS), 100 primary IBS (pIBS) care patients, and 100 patients with active inflammatory bowel disease (IBD). Patients were asked if they had either seriously contemplated or attempted suicide specifically because of their bowel problem as opposed to other issues. The hospital anxiety depression score was recorded, as were other clinical details on all patients.

RESULTS

A total of 38% of tIBS patients had contemplated suicide because of their symptoms compared with 16% and 4% in the sIBS and pIBS groups (tIBS vs. sIBS vs. pIBS, P = .002, P < .001). The figure for IBD was 15% (tIBS v. IBD, P < .001). Five tIBS and 1 IBD patient had attempted suicide for gastrointestinal reasons. Mean depression scores did not exceed threshold (10) in the sIBS group contemplating suicide (9.7), but were increased in the equivalent tIBS group (11.7). Hopelessness because of symptom severity, interference with life, and inadequacy of treatment were highlighted as crucial issues for all IBS patients.

CONCLUSIONS

IBS has the potential for a fatal outcome from suicide with depression not accounting for all the variance in suicidal ideation. Our observations emphasize the level of hopelessness felt by these patients and the need for improvement in the services provided to them.

Review article: epidemiology and quality of life in functional gastrointestinal disorders

The epidemiology and health-related quality of life associated with functional gastrointestinal disorders are reviewed, with particular emphasis on irritable bowel syndrome and functional dyspepsia. The literature supports the significant world-wide prevalence of functional gastrointestinal disorders, including irritable bowel syndrome (IBS), functional dyspepsia and chronic constipation. An increased female prevalence has been demonstrated in most studies in patients with IBS and chronic constipation, but not functional dyspepsia. The female to male ratio appears to be greater in the health care-seeking population than in community populations. However, some differences in the reported general prevalence and gender-related prevalence of functional gastrointestinal disorders may be due to cultural factors and study methodology. A significant health care burden is associated with IBS, with increased out-patient services, abdominal and pelvic surgeries, and gastrointestinal- and non-gastrointestinal-related physician visits and health care costs. Health-related quality of life is impacted significantly in patients with functional gastrointestinal disorders, such as functional dyspepsia and IBS, compared with the general healthy population, as well as patients with other chronic medical conditions, such as gastro-oesophageal reflux disease and asthma. Impaired health-related quality of life has been demonstrated, in particular, in patients with moderate to severe disease seen in referral settings. The health-related quality of life appears to improve in treatment responders, or correlates with symptom improvement, with at least some treatment modalities studied in functional gastrointestinal disorders, but further studies are needed. Predictors of health-related quality of life in patients with functional gastrointestinal disorders include psychosocial factors, such as early adverse life events, and symptoms related to visceral perception, e.g. pain and chronic stress. The presence of extra-intestinal symptoms appears to have a major if not greater impact on health care visits, excess health care costs and health-related quality of life in patients with functional gastrointestinal disorders.

Review article: the overlap between functional dyspepsia and irritable bowel syndrome -- a tale of one or two disorders?

Functional dyspepsia and irritable bowel syndrome are currently considered to be two separate nosological entities. However, the overlap of symptoms and the evidence of a number of common pathophysiological characteristics suggest that functional dyspepsia and irritable bowel syndrome may be different presentations of the same disorder. In this review, we critically appraise points in common, as well as differences, in the epidemiology, pathophysiology and response to treatment of functional dyspepsia and irritable bowel syndrome. Population-based studies and large case series show that one- to two-thirds of subjects with irritable bowel syndrome have symptoms that overlap with functional dyspepsia. Symptom analyses have generally failed to support functional dyspepsia and irritable bowel syndrome as separate entities. An exaggerated motor response to meals, delayed gastric emptying and abnormal small bowel and colonic transit can all be found in subsets of functional dyspepsia and irritable bowel syndrome, and are not exclusive to either condition. Visceral hypersensitivity is a common feature to both entities and seems unlikely to be site or disease specific. There is good evidence for the post-infectious development of irritable bowel syndrome, and this may also apply in functional dyspepsia. Psychiatric comorbidities are similar in functional dyspepsia and irritable bowel syndrome. Several common drug classes (prokinetics, visceral analgesics, psychoactive agents) may similarly improve both functional dyspepsia and irritable bowel syndrome symptoms. The evidence available suggests that at least subsets of functional dyspepsia and irritable bowel syndrome represent different manifestations of a single entity. The identification of common pathophysiological targets for therapy should be pursued in future research.

Irritable bowel syndrome in France: a common, debilitating and costly disorder

OBJECTIVE

This epidemiological investigation aims to measure the prevalence of irritable bowel syndrome (IBS) in the general population using the Rome II criteria and to evaluate the medical management including treatments and the impact of IBS on patient life.

METHODS

A nationally representative sample of 20,000 French subjects, aged 18 years and over, were interviewed by SOFRES (French Public Opinion Poll Institute) in May 2001. In a second phase (June/July 2001), a 48-question self-administered questionnaire was given to the subjects who have been selected during the first phase as suffering from IBS (Rome II criteria).

RESULTS

The prevalence of IBS was 4.7% (confidence interval, 4.36-5.04% with 5% risk) with a predominance in women (5.7% versus 3.7%, P < 0.01). The abdominal pain was often longstanding (> 5 years, 50%), intense (43%) and nocturnal (35%). During the most recent painful episode the levels of associated transit problems were almost equally divided between diarrhoea (36%), constipation (29%) and alternate episodes of both (31%). Apart from pain, bloating was given as the most frequent (73%) and most troublesome (24%) symptom. Since the onset, 80% of subjects with IBS had consulted a doctor (90% consulted a general physician, 57% a gastroenterologist, 50% both) and of these, 80% consulted within the previous 12 months. Sixty-seven per cent of subjects underwent additional investigations since the start of their illness (average of 3.4 examinations per patient examined: colonoscopy, 34.1%; laboratory tests, 34%; and abdominal ultrasound, 27.7%). Over the previous 12 months, 8% of the subjects had been admitted to hospital (average length of stay, 6.6 days), 11% of employed subjects had to take time off, 93% of subjects had taken prescribed medication (87%), but 43% of people thought it was ineffective. The effect on daily life was considerable (score, 6.2/10; close to the score for flu, 7/10). Two-thirds of the individuals changed their diet; 54% said it affected their social life and 29% their professional life. Seventy-four per cent of patients trusted their doctor, with a satisfaction index of 63%, but 45% of patients would like to have more information on IBS.

CONCLUSION

This study confirmed that the Rome II criteria detected IBS with a prevalence of 4.7%. The recruited subjects had severe symptoms (frequency, intensity and duration) that had a considerable effect on their daily life. The high level of referrals and initial consultations in all categories and the patient's attitudes towards the illness and its treatment emphasize the relative ineffectiveness of care for patients suffering from IBS.

Age-related decline in rectal mucosal lymphocytes and mast cells

BACKGROUND

Previous studies have shown that irritable bowel syndrome declines with age and is more common in women. Recent reports suggest that some diarrhoea predominant irritable bowel syndrome patients have low-grade inflammation with increased numbers of mucosal T lymphocytes, 5-hydroxytryptamine (5-HT) containing enteroendocrine cells and mast cells.

OBJECTIVE

To determine whether there are age or gender-related changes in mucosal T lymphocytes, mast cells or enteroendocrine cells which might explain these findings.

METHODS

Forty healthy volunteers (20 subjects below 55 years of age and 20 above 55 years) free from gastro-intestinal symptoms or disease answered detailed bowel symptom questionnaires and underwent sigmoidoscopy, rectal biopsy and colonic transit measurement. Biopsies were immunostained and quantified for lamina propria and intra-epithelial T lymphocytes, mast cells and 5-HT and peptide YY enteroendocrine cells.

RESULTS

There was a reduction in lamina propria T lymphocyte counts (P = 0.018), crypt intra-epithelial T lymphocytes (P = 0.014) and mast cells (P = 0.02) in the > 55 year group. Enteroendocrine cell numbers did not decline with age and were not related to colonic transit. There were no gender differences between any of the cells quantified.

CONCLUSIONS

Lymphocyte and mast cell numbers decline with age in normal large bowel mucosa. Reduced numbers of mucosal inflammatory cells may influence the low-grade inflammatory response to luminal antigens and contribute to the reduction of irritable bowel syndrome observed in older subjects.

Ovarian hormone modulates 5-hydroxytryptamine 3 receptors mRNA expression in rat colon with restraint stress-induced bowel dysfunction

AIM: To examine the effects of ovarian hormone on the expression of 5-hydroxytryptamine 3 receptors (5-HT₃R) in rat colon of restraint stress-induced bowel dysfunction.

METHODS: Twenty-four female Sprague-Dawley rats were randomly divided into three groups of 8 each: sham operation, ovariectomy (OVX) and ovariectomy with estrogen (E₂) and progesterone (P) replacement therapy (OVX+E₂+P). The rats were subjected to 1-h restraint stress 4 wk after operation. The changes of defecation were monitored by collection of fecal pellets. The gonadal steroids were measured in duplicate by radioimmunoassay (RIA). The expression of 5-HT₃R mRNA in the colon was studied by RT-PCR.

RESULTS: Compared with sham group and OVX+E₂+P group, OVX group showed increase in fecal pellets and decrease in the time of vitreous pellets excretion (P < 0.01). Serum levels of E₂ and P were suppressed in OVX group and restored following treatment with ovarian steroids (P < 0.01), and the levels of 5-HT₃R mRNA in the colon of ovariectomized rats were significantly increased, the expression of 5-HT₃R mRNA was significantly decreased in hormone replacement therapy group (P < 0.01).

CONCLUSION: Ovarian hormone plays a role in the regulation of 5-HT₃R expressions in restraint stress-induced bowel dysfunction of rats. The interactions between ovarian steroids and gastrointestinal tract may have major pathophysiological implications in 5-HT-related disorders, such as irritable bowel syndrome (IBS).

Epidemiological features of irritable bowel syndrome in a Turkish urban society

BACKGROUND AND AIM

Irritable bowel syndrome (IBS) is a widespread functional bowel disorder and its prevalence in Western societies ranges from 3-20%. The present study aimed to determine the prevalence of IBS in eastern Turkey, particularly in urban parts of Elazig where 250 000 people live.

METHODS

Of the 18 primary care centers, four were randomly selected for this study. All individuals (aged >17 years) living around the service area of these health centers were included. A total of 1900 subjects were randomly selected using the personal health records from the primary care centers. The total number of subjects that could be contacted was 1766. A questionnaire with multiple choice questions was applied to the subjects by medical students using the face-to-face technique. Prevalence of IBS and distribution of symptoms were evaluated by the Rome II criteria.

RESULTS

Of the 1766 subjects, 45.4% were male and 54.6% were female. Prevalence of IBS was 5% in males, 7.4% in females and 6.3% overall. The percentage of subjects with IBS in the 17-30 years age group was 26.2%; 52.3% in the 30-50 years age group and 21.6% in the above 50 years age group. Prevalence of IBS was highest (10.2%) in persons who were illiterate and lowest (3.0%) in university graduates. A positive correlation was determined between low economical status and prevalence of IBS (P < 0.05).

CONCLUSION

Although IBS is widely present in Turkey, its prevalence is lower than that reported in Western communities. In the region where this study was carried out, IBS was more prevalent in females and in individuals with low educational and economical status.

Irritable bowel syndrome - an evidence-based approach to diagnosis

Irritable bowel syndrome (IBS) represents one of the most common reasons for primary care visits and consultation with a gastroenterologist. It is characterized by abdominal discomfort, bloating and disturbed defecation in the absence of any identifiable physical, radiologic or laboratory abnormalities indicative of organic gastrointestinal disease. IBS is a costly disorder, responsible for significant direct and indirect costs to patients and society. Much of the cost attributed to IBS arises from the time and resources used to establish the diagnosis. Historically IBS has been viewed by many as a diagnosis of exclusion rather than as a primary diagnosis, and many patients with typical symptoms will undergo an extensive array of diagnostic tests and procedures prior to the eventual diagnosis of IBS. Recent reviews addressing the management of such patients have cast doubt on the necessity for this degree of testing. Current best evidence does not support the routine use of blood tests, stool studies, breath tests, abdominal imaging or lower endoscopy in order to exclude organic gastrointestinal disease in patients with typical IBS symptoms without alarm features. Serological testing for celiac sprue in this population may eventually prove useful but validation of studies indicating an increased prevalence of this disease in patients with suspected IBS is needed. The development and refinement of symptom-based criteria defining the clinical syndrome of IBS has greatly facilitated the diagnosis of this condition, which can be confidently diagnosed through the identification of typical symptoms, normal physical examination and the exclusion of alarm features. The presence of alarm features or persistent non-response to symptom-directed therapies should prompt a more detailed diagnostic evaluation dictated by the patient's predominant symptoms.

Effects of mu and kappa opioid receptor agonists and antagonists on contraction of isolated colon strips of rats with cathartic colon

AIM: To study the effects of mu and kappa opioid receptor agonists and antagonists on the isolated colon strips of rats with cathartic colon.

METHODS: Cathartic colon model was established by feeding rats with contact laxatives, and effects of mu and kappa opioid receptor agonists and antagonists on electricity-stimulated contraction of isolated colon strips of rats with cathartic colon were observed.

RESULTS: Compared with control group, exogenous mu and kappa agonists inhibited significantly electricity-stimulated contraction of strips of cathartic colon (8.50 ± 0.89 mm, 6.24 ± 0.91 mm, 3.35 ± 0.6 mm vs 11.40 ± 0.21 mm P < 0.01; 8.98 ± 0.69 mm, 6.89 ± 0.71 mm, 4.43 ± 0.99 mm vs 11.40 ± 0.21 mm, P < 0.01). In contrast, the exogenous mu antagonist significantly enhanced electricity-stimulated contraction of isolated colon strips (13.18 ± 0.93 mm, 15.87 ± 0.98 mm, 19.46 ± 1.79 mm vs 11.40 ± 0.21 mm, P < 0.01), but kappa antagonist had no effect on the isolated colon strips of rats with cathartic colon.

CONCLUSION: Mu and kappa opioid receptors are involved in the regulation of colon motility of rats with cathartic colon.

Management of irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders. The prevalence rate is 10-20% and women have a higher prevalence. IBS adversely affects quality of life and is associated with health care use and costs. IBS comprises a group of functional bowel disorders in which abdominal discomfort or pain is associated with defecation or a change in bowel habit, and with features of disordered defecation. The consensus definition and criteria for IBS have been formalized in the "Rome II criteria". Food, psychiatric disorders, and gastroenteritis are risk factors for developing IBS. The mechanism in IBS involves biopsychosocial disorders; psychosocial factors, altered motility, and heightened sensory function. Brain-gut interaction is the most important in understanding the pathophysiology of IBS. Effective management requires an effective physician-patient relationship. Dietary treatment, lifestyle therapy, behavioral therapy, and pharmacologic therapy play a major role in treating IBS. Calcium polycarbophil can benefit IBS patients with constipation or alternating diarrhea and constipation.

CRF1 receptor signaling pathways are involved in stress-related alterations of colonic function and viscerosensitivity: implications for irritable bowel syndrome

1. The characterization of corticotropin releasing factor (CRF) and, more recently, the discovery of additional CRF-related ligands, urocortin 1, urocortin 2 and urocortin 3, the cloning of two distinct CRF receptor subtypes, 1 (CRF(1)) and 2 (CRF(2)), and the development of selective CRF receptor antagonists provided new insight to unravel the mechanisms of stress. Activation of brain CRF(1) receptor signaling pathways is implicated in stress-related endocrine response and the development of anxiety-like behaviors. 2. Compelling evidence in rodents showed also that both central and peripheral injection of CRF and urocortin 1 mimic acute stress-induced colonic response (stimulation of motility, transit, defecation, mucus and watery secretion, increased ionic permeability and occurrence of diarrhea) in rodents. Central CRF enhances colorectal distention-induced visceral pain in rats. Peripheral CRF reduced pain threshold to colonic distention and increased colonic motility in humans. 3. Nonselective CRF(1)/CRF(2) antagonists and selective CRF(1) antagonists inhibit exogenous (central or peripheral) CRF- and acute stress-induced activation of colonic myenteric neurons, stimulation of colonic motor function and visceral hyperalgesia while selective CRF(2) antagonists have no effect. None of the CRF antagonists influence basal or postprandial colonic function in nonstressed animals. 4. These findings implicate CRF(1) receptors in stress-related stimulation of colonic function and hypersensitivity to colorectal distention. Targeting CRF(1)-dependent pathways may have potential benefit against stress or anxiety-/depression-related functional bowel disorders.

Pathophysiology as a basis for understanding symptom complexes and therapeutic targets

Sensorimotor disorders of the stomach, small intestine and colon have a limited repertoire of clinical manifestations, and there is the potential for more than one mechanism to lead to symptoms. In many recent clinical trial programs of novel agents in neurogastroenterology, the emphasis has been primarily on symptom assessment of broad groups of patients identified by the Rome criteria. Drugs of potential value have fallen by the wayside with this approach. We propose the current paradigm is partly to blame; physiological testing should provide the basis for identifying more homogeneous populations and therapeutic targets within functional bowel disease, and this applies to the upper and lower gut. Here we summarize the evidence that certain biomarkers can, in a limited fashion, be used to predict the success of an experimental medicine in common disorders of gastrointestinal function, including the irritable bowel syndrome and functional dyspepsia. Although the current evidence is limited and is most convincingly demonstrated with examples of transit measurements (for loperamide, alosetron, tegaserod and piboserod), we perceive this paradigm that studies using validated and responsive biomarkers have an important role to play in drug development.

Treating irritable bowel syndrome: overview, perspective and future therapies

This article summarizes the ongoing challenges in irritable bowel syndrome and the exciting opportunities for development of novel therapies for this common, enigmatic condition. The challenges include insufficient understanding of mechanisms, lack of specificity of symptoms, differentiation from other conditions, and lack of availability of noninvasive tests to identify dysfunctions. However, significant opportunities are reflected by the advances in clinical trial design and, particularly, clinically relevant end points for such trials, and the increasing understanding of basic neuroenteric science. The latter has delivered two new medications to the practice (alosetron and tegaserod), and other candidate therapies (other serotonergic, tachykininergic, opioid, cannabinoid modulators) are being carefully appraised as potential drugs for the future.

Activated mast cells in proximity to colonic nerves correlate with abdominal pain in irritable bowel syndrome

BACKGROUND & AIMS

The mechanisms underlying abdominal pain perception in irritable bowel syndrome (IBS) are poorly understood. Intestinal mast cell infiltration may perturb nerve function leading to symptom perception. We assessed colonic mast cell infiltration, mediator release, and spatial interactions with mucosal innervation and their correlation with abdominal pain in IBS patients.

METHODS

IBS patients were diagnosed according to Rome II criteria and abdominal pain quantified according to a validated questionnaire. Colonic mucosal mast cells were identified immunohistochemically and quantified with a computer-assisted counting method. Mast cell tryptase and histamine release were analyzed immunoenzymatically. Intestinal nerve to mast cell distance was assessed with electron microscopy.

RESULTS

Thirty-four out of 44 IBS patients (77%) showed an increased area of mucosa occupied by mast cells as compared with controls (9.2% +/- 2.5% vs. 3.3 +/- 0.8%, respectively; P < 0.001). There was a 150% increase in the number of degranulating mast cells (4.76 +/- 3.18/field vs. 2.42 +/- 2.26/field, respectively; P = 0.026). Mucosal content of tryptase was increased in IBS and mast cells spontaneously released more tryptase (3.22 +/- 3.48 pmol/min/mg vs. 0.87 +/- 0.65 pmol/min/mg, respectively; P = 0.015) and histamine (339.7 +/- 59.0 ng/g vs. 169.3 +/- 130.6 ng/g, respectively; P = 0.015). Mast cells located within 5 microm of nerve fibers were 7.14 +/- 3.87/field vs. 2.27 +/- 1.63/field in IBS vs. controls (P < 0.001). Only mast cells in close proximity to nerves were significantly correlated with severity and frequency of abdominal pain/discomfort (P < 0.001 and P = 0.003, respectively).

CONCLUSIONS

Colonic mast cell infiltration and mediator release in proximity to mucosal innervation may contribute to abdominal pain perception in IBS patients.

Tegaserod for the treatment of irritable bowel syndrome

BACKGROUND

IBS is a complex disorder that encompasses a wide profile of symptoms. Current drug treatments for irritable bowel syndrome (IBS) are of limited value. Many target specific symptoms only. Tegaserod, a 5HT(4) partial agonist, represents a novel mechanism of action in the treatment of IBS.

OBJECTIVES

The objective of this review was to evaluate the efficacy and tolerability of tegaserod for the treatment of IBS in adults and adolescents aged 12 years and above.

SEARCH STRATEGY

MEDLINE 1966-November 2002 and EMBASE 1980-November 2002 were searched. The text and key words used included "tegaserod", "HTF 919", "irritable bowel", and "colonic diseases, functional". The Cochrane Central Register of Controlled Trials, the Inflammatory Bowel Disease Review Group Specialized Trials Register, and Science Citation Index were also searched. Proceedings from the British Society of Gastroenterology Annual Meeting, and Digestive Disease Week (1998-2002) were hand searched. The manufacturer of tegaserod was contacted. Relevant articles were retrieved, and their reference lists were also reviewed.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials comparing tegaserod with placebo, no treatment or any other intervention (pharmacological or non-pharmacological) in subjects aged 12 years and above with a diagnosis of IBS, focusing on clinical endpoints were considered for review.

DATA COLLECTION AND ANALYSIS

Study inclusion and exclusion, data extraction and quality assessment was undertaken by two reviewers independently. Meta-analysis was performed where study populations, designs, outcomes, and statistical reporting allowed combination of data in a valid way, using the summary statistic relative risk with 95% CI. Eight short-term placebo-controlled studies fulfilled our inclusion criteria. These were predominantly conducted in women. Seven studies evaluated the efficacy of tegaserod on global gastrointestinal (GI) symptoms in patients with constipation-predominant IBS (C-IBS). One small study evaluated safety in patients with diarrhoea-predominant IBS.

MAIN RESULTS

The relative risk (RR) of being a responder in terms of global relief of GI symptoms was significantly higher with tegaserod 12 mg (RR 1.19, 95% CI 1.09, 1.29) and tegaserod 4 mg (RR 1.15, 95% CI 1.02, 1.31) compared with placebo, with a number needed to treat (NNT) of 14 and 20 respectively. When all tegaserod doses were combined and compared with placebo (n=4040), the RR of being a responder was 1.17 (95% CI 1.08, 1.27), with a NNT of 17. Although the pooled results indicate statistically significant benefit with tegaserod, the a priori minimal clinically important differences set in two of the four pooled studies were not reached. Tegaserod did not significantly improve the patients' individual symptoms of abdominal pain and discomfort although bowel habit showed a statistically significant improvement with tegaserod 4 mg and there was a non-significant trend in favour of tegaserod 12 mg. When GI symptoms were assessed separately, those indicative of GI motility such as number of bowel movements and days without bowel movements were generally improved with tegaserod although the proportion of patients experiencing diarrhoea was significantly higher in the tegaserod 12 mg group compared with placebo (RR 2.75, 95% CI 1.90, 3.97), with a number needed to harm (NNH) of 20. Effects of tegaserod on GI symptoms such as bloating, stool consistency, and straining were not consistent across the studies.

REVIEWER'S CONCLUSIONS

Tegaserod appears to improve the overall symptomatology of IBS but there are currently few data on its effect on quality of life. In addition, more information is needed about its efficacy in men. It would also be of interest to know whether treatment with tegaserod leads either directly, or indirectly, to changes in visceral sensitivity or psychopathology, which are also considered important in the pathophysiology of this condition.

Influence of sex and experimental protocol on the effect of maternal deprivation on rectal sensitivity to distension in the adult rat

Neonatal maternal separation induces visceral hyperalgesia before and after stress in male rats. This study compares the effects on sensitivity to rectal distension in adult male and female rats, using two protocols of deprivation. Between postnatal days 1 and 14, maternal deprivation was performed for 2 h per day according to a protocol of type M (removal of all pups from home cage) or type P (separation of half of littermates). Visceral sensitivity was assessed at 12 weeks of age by the number of abdominal contractions induced by rectal distension before and after restraint stress. Calcitonin gene-related peptide (CGRP) was identified in the rectal wall by immunohistochemistry. In basal conditions, both separation protocols induced hyperalgesia, that was greater after type M than type P, and in females than in males for type P separation. Acute restraint stress induced hyperalgesia in control females only, and this effect was similarly enhanced by both type P and M separation. No difference was found between controls and deprived rats in rectal CGRP immunoreactivity which was greater in females and increased after rectal distension. These results indicate that long-term visceral hyperalgesia depends upon the type of maternal deprivation and that females are more sensitive than males.